Microwave dielectric properties calculation of Si2N2O/BN composites based on mixture equations

The propagation-wave radome materials have been widely used in rockets, spaceships, missiles and other flying weapons equipment, and with the improvement of the service conditions of flying weapons equipment (such as long-term high temperature environment), more and more attention has been paid $\mathrm{Si}_{2} \mathrm{~N}_{2} \mathrm{O}$ composites because it has low density, dielectric constant, dielectric loss, high hardness, decomposition temperature, oxidation resistance and heat resistance and other excellent properties in the research field of high temperature propagation-wave materials. In this paper, the microwave dielectric constant and loss of $\mathrm{Si}_{2} \mathrm{~N}_{2} \mathrm{O}$ and BN ceramics are tested by resonant cavity method, and the dielectric constants of $\mathrm{Si}_{2} \mathrm{~N}_{2} \mathrm{O} / \mathrm{BN}$ composites are compared and analyzed by several mixture theoretical models. It is found that the dielectric constant of $\mathrm{Si}_{2} \mathrm{~N}_{2} \mathrm{O} / \mathrm{BN}$ composite ceramics is positively correlated with the content of $\mathrm{Si}_{2} \mathrm{~N}_{2} \mathrm{O}$ and negatively correlated with the amount of BN, that is, the larger the amount of BN added, the smaller the dielectric constant of the composite material. Moreover, the Maxwell-Wagner equation and logarithmic law theoretical model are more suitable for the prediction of the dielectric properties of composites, which is suitable for the study of the thermoelectric behavior of this kind of composite ceramics.